Its main offices are in Lyon, France. Its role is to conduct and coordinate research into the causes of cancer. It also collects and publishes surveillance data regarding the occurrence of cancer worldwide.[2] It maintains a series of monographs on the carcinogenic risks to humans posed by a variety of agents, mixtures and exposures.[3] Following its inception, IARC received numerous requests for lists of known and suspected human carcinogens. In 1970, the IARC Advisory Committee recommended that expert groups prepare a compendium on carcinogenic chemicals, and it began publishing its monographs series with this aim in mind.[4]

On 26 October 2015, IARC reported that consumption of processed meat (such as bacon, ham, hot dogs, sausages) was a Class 1 carcinogen, and that red meat was a Class 2A carcinogen ("probably carcinogenic to humans").[5][6][7]

The IARC categorizes agents, mixtures and exposures into five categories. Note that the classification is based only on the strength of evidence for carcinogenicity, not on the relative increase of cancer risk due to exposure, or on the amount of exposure necessary to cause cancer. For example, a substance that only very slightly increases the likelihood of cancer and only after long-term exposure to large doses, but the evidence for that slight increase is strong, would be placed in Group 1 even though it does not pose a significant risk in normal use.[8]

Group 1: carcinogenic to humans: There is enough evidence to conclude that it can cause cancer in humans.

Group 2A: probably carcinogenic to humans: There is strong evidence that it can cause cancer in humans, but at present it is not conclusive.

Group 2B: possibly carcinogenic to humans: There is some evidence that it can cause cancer in humans but at present it is far from conclusive.

Group 3: not classifiable as to carcinogenicity in humans: There is no evidence at present that it causes cancer in humans.

Group 4: probably not carcinogenic to humans: There is strong evidence that it does not cause cancer in humans. Only one substance – caprolactam – has been both assessed for carcinogenicity by the IARC and placed in this category.

Critics of the IARC have stated that it has become susceptible to industry influence and suffers from a lack of transparency. Lorenzo Tomatis, its director from 1982 to 1993, was "barred from entering the building" in 2003 after "accusing the IARC of softpedaling the risks of industrial chemicals"[9] in a 2002 article.[10] In 2003 thirty public-health scientists signed a letter targeting conflicts of interest and the lack of transparency.[9] The IARC rejected these criticisms, and there was hope that the controversy would "die down" after Paul Kleihues (Director from 1994) retired in 2004 and Peter Boyle became the new director, followed by Christopher Wild since 2009.[9]

Tomatis focused on the IARC monographs which rate chemical's carcinogenicity, and cited several cases in his 2002 critique. In 1998 a panel voted 17-13 to rate 1,3-butadiene a carcinogen. A second vote which Tomatis called "highly irregular" occurred after "industry observers schmoozed with the panelists and one panelist left the meeting", and a 15-14 vote downgraded the chemical to a "possible carcinogen".[9] Joan Denton, director of California's Office of Environmental Health Hazard Assessment, made accusations in relation to styrene in 2002,[9] and Michael Jacobsen of the Center for Science in the Public Interest criticized the inclusion of industry observers in a saccharin panel, who were allowed to vote.[9] Tomatis has also highlighted Bis(2-ethylhexyl) phthalate.[11] In defense of the IARC, Kleihues noted that only 17 of 410 of the working-group participants were consultants to industry and these people never served as chairs. He said that "people who receive funds from affected agencies do not vote", and further noted that industry-funded scientists are important because industry often funds studies.[9]

IARC's secrecy led a Lancet Oncology editorial to warn of the agency's eroding reputation. As of 2003 the IARC did not release details of disputed votes, did not release the financial disclosure forms required of panelists, or the names of the panelists until the panel is complete. Individuals being considered for the new director are released only to representatives from the sixteen member countries. Kleihues and other agency officials defend the IARC, with Kleihues noting that procedures and names are listed on the finished monographs, and said names are not released to avoid political pressures. The IARC was considering new transparency disclosures such as a "narrative" explaining disputed votes.[9]

Ed Yong, a British science journalist, has criticized the agency and its "confusing" category system for misleading the public.[12] Marcel Kuntz, a French director of research at the French National Centre for Scientific Research, criticized the agency for its classification of potentially carcinogenic substances. He claimed that this classification did not take into account the extent of exposure; for example, red meat is qualified as probably carcinogenic, but the quantity of consumed red meat at which it could become dangerous is not specified.[13]

On 20 March 2015, IARC announced that it had evaluated the carcinogenicity of five different pesticides and published its findings in The Lancet Oncology as well as Volume 112 of the IARC Monographs.[14] One of the substances, the herbicide glyphosate, was classified as "probably carcinogenic to humans" and put into the IARC's Group 2A.[14] Glyphosate the key ingredient in, and is sold under the brand name of Roundup, which is sold by the company Monsanto. It is one of the most heavily used weedkillers in the world.[15][16]

In early 2016, IARC was issued legal requests related to its work with glyphosate. In April 2016, internal IARC officials told its experts to not release documents or comply with the legal requests related to its review of glyphosate.[16] At the time, the global movement against genetically modified crops (GMO) targeted glyphosate in a public relations and protest campaign.[15] According to The Hill, there are hundreds of studies that confirm that glyphosate is safe.[15]

Some of the items that the IARC classifies as carcinogens, such as coffee, mobile phones, and processed meat have caused controversy.[17][16] Included in its list of carcinogens are "drinking hot beverages" and "working as a hairdresser."[15]

The controversy over glyphosate extends worldwide. The IARC is currently in a dispute with the European Food Safety Authority, United Nations and United States regulators over its classification of glyphosate as a carcinogen.[17] In the summer of 2015, the European Union debated for several months over the use of glyphosate. Some countries such as France and Germany were in opposition.[15] Additionally, regulators in the U.S., Europe, Canada, Japan and New Zealand have said that glyphosate is not likely to pose a risk of cancer to people.[16]

IARC's decision regarding glyphosate has a far-reaching impact, however. California put glyphosate on its list of unsafe chemicals based on the fact that the IARC reported it as a carcinogen.[15] In September 2016 the U.S. Environmental Protection Agency (EPA) withdrew a report that it had initially stamped as "final", a report that had said that glyphosate was not a carcinogen.[18]

The IARC is the only agency that classifies glyphosate as carcinogenic.[15]

In the fall of 2016, the U.S. House Committee on Oversight and Government Reform held a briefing to ask officials from the National Institutes of Health (NIH) about NIH's grant funding to the IARC.[19] Chairman Jason Chaffetz (R-UT) questioned the director of the NIH to explain why federal dollars support what Chaffetz referred to as a flawed agency.[15] The NIH grant database shows that it has given the IARC over $1.2 million in 2016. Chaffetz asked the NIH to give his committee details of its standards for awarding grants and vetting grant nominees.[17]

Additionally, Congressman Robert Aderholt, chairman of the House Appropriations Subcommittee on Agriculture, wrote a letter in June 2016 to the head of the NIH questioning the funding of IARC.[17]

During its half century in existence, the IARC has assessed nearly 1,000 substances. Out of those 1,000 substances it classified 999 as carcinogenic and 1 as non-carcinogenic.[15] Critics of the IARC have said that the organization is too fast to conclude that substances are carcinogenic. As a result, critics say, unnecessary health scares break out. However, the IARC says that its methods are scientifically sound.[17]

One argument against IARC's methodology comes from the American Chemistry Council (ACC). ACC said in a news article published in Chemistry World (which is published by the Royal Society of Chemistry in Great Britain) that the IARC evaluates how hazardous a substance is based on whether the substance could "cause cancer in humans under any circumstances, including at exposure levels beyond what is typical."[19] Another argument is that the IARC's monograph process is based on a scientific concept from the 1970s, and that it only separates substances into two broad categories: carcinogens and non-carcinogens.[20] In the fall of 2016, 10 scientists wrote a commentary saying that they believed the IARC uses an outdated model of "hazard-based assessments" when determining whether a substance is a human carcinogen. They wrote, "This is how eating processed meat can fall into the same category as sulfur mustard gas." One of the scientists is a former science adviser to the U.S. Environmental Protection Agency. The scientists proposed that IARC update its methodology to the principles and concepts of "existing international consensus-based frameworks" such as the framework used by the World Health Organization International Programme on Chemical Safety.[20]

The IARC says that it found that glyphosate is linked to only one type of cancer, non-Hodgkin's lymphoma.[15] The main argument in support of IARC's methodology comes from the director of IARC, Chris Wild.[19] According to Wild, IARC has more than 40 years of experience evaluating carcinogens and that the IARC's monographs are "widely respected for their scientific rigor, standardized and transparent process and for freedom from conflicts of interest."[16] Wild also said that the IARC only chooses substances to evaluate from which there already exists a body of scientific literature that says there is a carcinogenic risk to humans. Wild said that because IARC does not select substances at random, that is the reason it has such a low rate of determining a substance as not being cancer-causing.[19]